This invention relates generally to bandgap engineered semiconductor structures and more particularly the invention relates to structures having dimensions sufficiently small so as to confine carriers located therein and resulting in novel electronic and optical properties.
There has been considerable attention paid to quantum wires since their proposal by H. Sakaki in the Jap. J. Appl. Phys. 19, L735-738 (1980). More recently, Canham in Appl. Phys. Lett. 57, 1046 (1990) has observed strong photoluminescence in anodically etched silicon, or porous silicon. The structure of this silicon resembles a sponge, composed of a myriad of silicon quantum dots or intertwined quantum wires.
Considerable work has been done in light emission from silicon. Currently, group IV semiconductors (silicon and germanium) are not used in lasers and light emitting diodes even though the materials are widely used for their electrical properties. A silicon based light emitting diode or laser would be a tremendous boon to the semiconductor industry with speed significantly improved over those of electrical conduction. The current research in silicon light emission has been in the area of porous silicon of the type noted above.
It has also been shown that quantum wires may show significant improvements in transport properties over bulk semiconductors due to decreased Coulomb scattering. Many other novel effects related to the quantum confinement have been reported such as non-local bend resistance, the quenching of the Hall effect, and the oscillatory behavior of capacitance and conductivity. Further, the optical properties of porous silicon can be combined with the improved electrical property to function as sensors.
Heretofore, quantum wire superlattices in gallium arsenide/aluminum gallium arsenide have been proposed for 8-20 micrometer photodetectors. A theoretical study of p-i-n GaAs/AlGaAs quantum wire detectors proposes that they may perform better than bulk devices due to increased absorption of photons and the higher carrier mobilities therein. See D. L. Crawford et al., Applied Physics Letters, 58 (1991), p. 1629.
The present invention is directed to the fabrication of a quantum bridge structure whose length, width, and height can be controlled by processing parameters. The resulting structure can exhibit photoluminescence and electroluminescence which allows the device to function in a light emitter, light detector, conductive wire, and a sensor mode.